L4: Bacterial physiology

Question 1

what is the difference between bacterial total count and viable count ?

Answer 1

total count includes both dead and live bacteria while viable count only includes live

Question 2

describe the 4 phases of the bacterial growth graph.

Answer 2

+lag phase :
-a lot of metabolic activity but no division
-cell reaches its maximum size
-bacteria is still adapting to new environment

+Log phase:
-rapid division
- this is where antimicrobials act

+stationary phase:
- number of bacteria dividing = number of bacteria dying
- more toxins are being produced
-nutrient supply is running low
-irregular staining , sporulation and production of exotoxins

+death phase :
-marked decline in viable bacterial count

Question 3

what does mesophilic mean ?

Answer 3

ability of bacteria to only grow within temperature range of 25-40 ( most pathogenic bacteria)_

Question 4

what terms refer to bacteria that only grow in cold and what term refers to bacteria that only grow in hot temperature ?

Answer 4

psychrophilic (-20)
thermophillic (55-58)

Question 5

what do the following terms mean:
-obligate aerobes
-obligate anaerobes
-facultative anaerobes
-aerotolerant anaerobes
-capnophillic organism

Answer 5

-obligate aerobes : only grows in presence of oxygen

-obligate anaerobes : only grows in absence of oxygen

-facultative anaerobes : can grow in both aerobic and anaerobic conditions

-aerotolerant anaerobes : anaerobe that can tolerate small amounts of oxygen
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-capnophillic organism: organism that grows in presence of co2

Question 6

what pH range do most pathogenic bacteria grow in ?

Answer 6

7.2-7.6 , neutral to slightly alkaline ( neutrophiles)

Question 7

what is an example of an acidophile and an alkalophile ?

Answer 7

acidophile : lactobaccili

alkalophile: vibro cholrae

Question 8

what does too much drying do to bacteria ?

Answer 8

its lethal to the cells since bacteria is 80% water

Question 9

what are the minimum requirements for growth of bacteria ?

Answer 9

water
source of carbon
source of nitrogen
inorganic soils

Question 10

what are autotrophs ?

Answer 10

bacteria that can synthesize their own organic compounds ( no medical significance )

Question 11

what are heterotrophs ?

Answer 11

bacteria that rely on pre-formed organic compounds and cannot synthesize their own